Estimated reading time: 7 minutes
- South Africa’s soils and pastures are generally phosphate deficient.
- Phosphate is essential for energy circulation and utilisation, and it plays a key role in the body, such as regulating the body’s pH balance, osmotic pressure, ovum development, skeletal development, as well as cell differentiation and growth.
- Phosphate licks, also known as mineral licks, normally contain macrominerals such as calcium (12%), phosphorus (6%) as well as sulphur, potassium, magnesium and the trace elements copper, zinc, cobalt, manganese, iodine, iron and selenium.
- Sheep are usually less susceptible to phosphate deficiencies because they graze more selectively than cattle.
- When giving supplements to your herd, always plan according to the production stage of the animals and what the veld can provide. Consider the economy and production, supplement only the deficiencies, and allow the animals to make maximum use of your veld.
South Africa’s soils and pastures are generally phosphate deficient. While ample rain in many parts of the country has given us green and lush grazing, the higher precipitation may have caused phosphate to leach from the soil.
The bioavailability and absorption of phosphate sources will, depending on the phosphate available in green grazing, vary from 60 or even 70% in grain. Summer is characterised by sufficient energy and protein, but a lack of phosphate. Supplementing phosphate therefore remains essential.
Phosphate-containing licks are given in summer to meet livestock’s mineral requirements. It plays a key role in various metabolic functions. Phosphate supplements for sheep and cattle are essential for supporting optimal production and reproduction on especially green grazing (Orsmond, 2007). Approximately 80% of the phosphate in an animal’s body is found in its skeleton (for formation and maintenance of bones and teeth). Excess phosphate, along with a combination of proteins and fat, is circulated throughout the body in the form of organic salts.
Functions of phosphate
Phosphate comprises 22% of the mineral ash in an animal’s body – just less than 1% of bodyweight. It is present in every living cell and is essential for energy circulation and utilisation. Supplements containing high amounts of phosphate have a positive impact on livestock’s condition and performance, especially during the growing season, as well as during the dry season when high-quality roughage such as silage, crop residues and hay are available.
Roughage remains the basis of nutrition and must be available throughout. If only limited amounts of roughage are available, supplements will be ineffective and uneconomic (Köster, 2020). Phosphate given in winter must be accompanied by sufficient levels of energy and protein to prevent weight loss.
Phosphate plays a key role in the body – for instance, it regulates the body’s pH balance, osmotic pressure, ovum development (which affects fertility), skeletal development, as well as cell differentiation and growth.
Disadvantages of poor absorption
There is a direct relationship between phosphate, vitamin D and calcium (Ca), with all three having an influence on the metabolic processes of phosphorus (P) in the body. The Ca:P ratio must not exceed 2:1 and therefore requires careful monitoring and maintenance. Vitamin D is crucial for stimulating the phosphate transport system in the small intestine, as it speeds up phytase activity, thus boosting phosphate retention.
The type of phosphate source is an important consideration, especially when it comes to phosphate absorption. The digestibility of commercial dicalcium phosphate (DCP) sources and monocalcium phosphate (MCP) sources can vary from 80 to 90%.
Drinking water or feed containing higher levels of other minerals such as calcium, sodium, iron, aluminium or molybdenum can have a negative effect on phosphate absorption, leading to secondary phosphate deficiencies. If there isn’t enough phosphate in the feed ingested by animals, they will start extracting phosphate from their bones – a process known as demineralisation. This extracted phosphate is utilised for metabolic processes.
As a result of demineralisation, some cows will even suffer broken bones when bulls try to cover them. Although sustainable in the short term, phosphate deficiencies over the long term can lead to substandard condition, slower growth rate and poorer milk production, weaning weight and fertility.
Phosphate lick supplements in diets
Phosphate licks, also known as mineral licks, normally contain macrominerals such as calcium (12%), phosphorus (6%) as well as sulphur, potassium, magnesium and the trace elements copper, zinc, cobalt, manganese, iodine, iron and selenium. Animals will typically respond well to phosphate supplements when the grazing is actively growing and animals’ weight is increasing. If a phosphate supplement is given in conjunction with poor or low-quality roughage, it may result in a negative outcome.
Sheep are usually less susceptible to phosphate deficiencies because they graze more selectively than cattle. They recirculate any unused phosphate back to the rumen via their saliva.
Phosphate deficiencies are not limited to one species only. In layers, for instance, most of the phosphate is used for egg production. A phosphate deficiency can lead to reduced bodyweight and feed conversion efficiency, as well as weaker eggshell quality. Goats may suffer from stunted growth and chew on bones, stones, plastic or pipes (pica). The diets of dogs and cats usually contain sufficient levels of phosphorus. A diet that lacks phosphate may result in poor growth and rickets.
The following symptoms may occur in phosphate-deficient cattle: reduced feed intake; suppressed immunity; impaired muscle mass in weaner calves; suppressed appetite; impaired feed conversion efficiency; reduced milk production post calving; dull coat; stiff joints.
Ruminant phosphate requirements
Sheep and cattle have different needs when it comes to phosphate. In ruminants, the animals’ physiological status, its breed and the phosphate available in the grazing will determine how much phosphate must be supplemented. Non-pregnant sheep require 1 to 2g of phosphate per day and late-pregnant or lactating ewes 3 to 4g. A dry cow on green summer grazing needs 6g per day, a growing heifer requires 9g and a late-pregnant or lactating cow 12g.
Lactating or pregnant animals require proper care, and this applies to phosphate as well, given that it supports both foetal growth and the cow. In regions that are phosphate deficient, the amount should be increased by 3 to 4g per cow per day. Grass growth in all regions of the country is optimal from mid to late November. The best time to put out transitional licks for the normal period of six weeks is during this period (Meaker, 2020).
Cost of supplements
Cost definitely plays a role in the provision of phosphate supplements. Phosphate supplements are considered expensive, although the benefits often outweigh the expense – you might end up paying more if you decide to not give your animals the necessary phosphate supplements.
Cows experiencing a phosphate deficiency can lose up to 20% of their bodyweight. The calving percentage of 90% will consequently drop to 50%. This represents a 40% decrease in the calving percentage due to poor condition as well as the inability to conceive.
Phosphate supplements have several benefits, such as better weaning weights, increased calving percentages, milk production and growth.
Data from 16 trials was used to calculate the average calving percentage among cows that were given phosphate supplements versus cows in the control group that received no supplements. The findings showed that the phosphate supplemented cows recorded an 80% calving percentage compared to the 51% rate of the non-supplemented cows.
The study also showed that the weaning weights of the phosphate supplemented animals were 27% higher (Read et al., 1986). These figures speak volumes as to the economic effect of phosphate supplements. To calculate the cost of phosphate supplementation, the supplements animals receive daily must be considered.
Final thoughts
When giving supplements to your herd, always plan according to the production stage of the animals and what the veld can provide. Consider the economy and production, supplement only the deficiencies, and allow the animals to make maximum use of your veld. – Han-Mari Potgieter, nutritionist, Qpro Feeds, VKB
For more information and references, contact Han-Mari Potgieter at nelhanmari@gmail.com.
